The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
CDM events represent electrostatic discharges which happen in manual and automated production systems for electronic ICs. In production tools the IC may acquire electrical charges by many ways, such as, for example, by contact, friction, and/or induction from a nearby electrical field just to mention a few possible ways. When conductive parts of ICs come into contact with grounded equipment parts or parts with lower electrical potentials, the accumulated IC charges are free to discharge spontaneously. As a result, a relatively high discharge current (ESD event) may destroy or damage IC (see, e.g., FIGS. 1a and 1b).
The design of IC components usually incorporates special means (or particular components) for protection against ESD effects. The semiconductor industry has developed several standard methods for testing IC devices and defined their CDM ESD threshold parameters such as, e.g., withstand voltage and current amplitude. The applicable standards also detail the test apparatus requirements for automated IC CDM tests. These methods and devices are useful during IC designing stages, final testing for product certification, and failure analyses of damaged devices.
However, conventional technology suffers from various constraints and/or deficiencies as will be discussed below. A goal in accordance with various embodiments of this invention is to provide a method and apparatus for real time ESD event monitoring and calibration in IC production tools and manufacturing processes.
FIG. 1a illustrates a typical discharge model 100 of charged (IC) device CDM event in a tool or processing chamber. In FIG. 1a, the MiniPulse ESD detector 105 (or another type of ESD detector 105) intercepts the electromagnetic waves 140, and the Robot Placement Effector 115 (or another suitable type of robotic arm 115) places a charged device 125 into a test socket 130. The test socket 130 is typically placed on a suitable test bed 131, base 131, or another suitable platform 131. As the charged device 125 approaches the test socket 130, a discharge (ESD) occurs and the antenna 135 (coupled to the MiniPulse Detector 105) intercepts the waves 140 of the discharge event. In this example, the ESD event is a discharge 141 that takes place in a form of a spark between two conductive parts 125 and 130 that both differ in voltage potential. The conductive parts 125 and 130 and other semiconductor processing equipment may be in a tool or processing chamber 132 that may have any suitable size such as, for example, approximately 2×2 feet, 4×4 feet, or other dimensions.
A current problem with conventional technology is in the difficulty in calibrating an ESD detector. This difficulty is due to, for example, the challenge in providing the repeatability of the discharge events themselves. Other difficulties exist due to conditions imposed upon the radiated electrical field waveform by the materials and configuration of the process point itself. Therefore, the current technology is limited in its capabilities and suffers from at least the above constraints and deficiencies. Embodiments of the invention provide systems and methods for overcoming the difficulties in calibrating the ESD detectors.
FIG. 1b shows a screen shot of a typical example voltage/current waveform of a CDM electrostatic event where a discharge takes place in a form of a spark between two conductive parts. The top waveform 180 is an example output signal (current pulse) that is similar to an example output signal that is produced by a CDMES (Charged Device Model Event Simulator) as will be discussed below in accordance with an embodiment of the invention. The lower waveform 185 is an example MicroESD antenna 135 response to an incident propagating field.
In FIG. 1b, the top waveform 180 shows a pulse signal that is similar to a pulse signal that can also be generated and/or simulated from a CDMES device to be discussed below in accordance with an embodiment of the invention. The bottom waveform 185 shows the radiated signal being detected by the antenna 135 coupled to the MiniPulse detector 105. The MiniPulse detector 105 includes an electronic circuit that is capable of receiving the signal that is intercepted by the antenna 135. The electronic circuit will classify this signal as an ESD event 110 if the electronic circuit determines that this signal is an ESD event of interest based upon an ESD voltage and pulse duration threshold levels as also discussed below.